M22 x 2.5 tap drill size
19.5 mm
- Inches
- 0.7677
- Inch bit
- 49/64"
- Thread
- 77%
Drill a 19.5 mm hole before cutting an M22 thread with 2.5 mm pitch. The rule for metric taps is diameter minus pitch.
No metric bits? A 49/64" bit (0.7656 in) gives about 79% thread.
M22 x 2.5 thread and hole sizes
| Thread | M22, 2.5 mm pitch, coarse |
|---|---|
| Major diameter | 22 mm 0.8661 in |
| Tap drill | 19.5 mm 0.7677 in |
| Closest inch bit | 49/64" 0.7656 in |
| Clearance hole, close fit | 23 mm |
| Clearance hole, medium fit | 24 mm |
Why 19.5 mm
Subtract the pitch from the diameter: 22 minus 2.5 is 19.5 mm. That leaves 77% thread, the usual target for a cut tap.
More thread than that adds almost no strength and makes the tap much easier to break. In hard or tough material, go 0.1 mm larger.
Tools for this job
- M22 x 2.5 tap
- 19.5 mm drill bit
- Tap and drill set
- Drill bit size gauge
- Thread pitch gauge
- Cutting oil for tapping
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